There are numerous verbatim copies of memos that were exchanged between President Johnson, the civilian (state and defense departments), and many military officials involved in this long-drawn out, lengthy period. From these memos, McNamera explained the circumstances, strategy, and thinking behind himself and others in the political, historical, and Cold War context of the time.
He repeatedly (in my ignorant opinion) took honest and objective attempts to highlight and elucidate the (by his own admission many cases of faulty) reasoning behind why forces were there in the first place, and why escalation continued throughout the 1960s. Many Southeast Asian political factors external to Vietnam were factors in the decision to enter, escalate, and proceed, as the U.S. military did in this conflict.
Some factors were: Sukarno in Indonesia (who was later toppled), Mao Zedong's promotion of "perpetual world-wide struggle through revolution," the Domino Theory (which we now know as false, but then it was difficult to know), among many other Cold War events that took place in the decade of the 1960s. The Cuban Missile Crisis, construction of the Iron Curtain, airlifts to Berlin, Khrushchev stating "we will bury you," and the mistakenly held perception that there was a "Sino-Soviet" pact, when in fact, the two didn't like each other.
McNamera noted more than once that there were no "experts" on Vietnam and Southeast Asian historical, culture, and contemporary politics. They often consulted "experts" on the Soviets, Chinese, and other adversaries, who were often proved to be correct and were vital to the formulation and implementation of foreign and military policy. In Vietnam they chose to have no "experts" to turn to who knew the people. As McNamera noted, he and the military and administration didn't know very much at all about Vietnam, and its' history.
A major point McNamera commonly stated was the perception of Ho Chi Minh by senior American political and military officials. Was Ho Chi Minh: 1. a nationalist who wanted to unify his country and expel foreigners who had subjugated Vietnam for hundreds of years (who also happened to be a communist, in the likes of Tito, independent of Peking and Moscow), or was he 2. A communist, who was promulgating Vietnamese unification under communism not only in Vietnam but also in neighboring South Eastern Asian nations. 3. A part of both or neither of 1. or 2. The answer now leans toward number 1. quite heavily. Should they have been aware of this then? McNamera says "yes."
Although their decisions were terrible an important thing for the reader to be constantly be aware of is: the context of when these thoughts, strategies, and actions took place. The 1960s were from a radically different world than that of today. One can't even imagine, if compared to 2003. The 1960s were the most intense decade during the Cold War. Presently, to make more than a couple of assumptions or critiques of the decisions made back during the conflict can easily (although not necessarily)lead to the comparison of "apples & oranges."
McNamera probably wanted to expunge himself of some of the blame he's often been given by history regarding the disastrous foreign policy-making in Vietnam that still is referred to by some as "McNamera's War." This is in part, but not entirely, true of course. Pointing mainly and/or only to McNamera is big-time oversimplification.
How interesting it is that a civilian intellectual Auto Executive can all of a sudden become Secretary of Defense in a single day. After getting a phone call from JFK and receiving Kennedy's job offer, McNamera replied he wasn't qualified to be Secretary of Defense, whereas JFK rhetorically asked "who is?" The rest is history: go figure.
Communists are indeed rotten autocratic people who've failed miserably. Communism, Marxism, Leninism, Stalinism and Maoism was the biggest mistake of the 20th Century. Yes, if the Pentagon bureaucrats and civilian leaders had simply read a couple of books on Vietnamese history they might have had a more balanced view of the objectives of the Viet Minh, NVA, and let the chips fall where they knew they were going long before Saigon fell.